Bill Gates has been one of the world’s richest people for decades. To build a legacy beyond Microsoft — and to build a better world — in 2000 he and his wife launched the Bill & Melinda Gates Foundation, which has spent billions of dollars on numerous good causes.

The world’s largest private charity has had some great successes — helping sharply reduce the prevalence of malaria worldwide, for one. But the Gates Foundation’s efforts to improve U.S. public education haven’t gone as well as hoped, as Gates admitted in remarks last month at an education conference. As a result, he said the foundation is “evolving our education strategy” as it looks to invest close to $1.7 billion in U.S. public schools over five years.

While the Gates Foundation has funded many education initiatives, its biggest splash came with its Common Core campaign, launched in 2009. Forty-two states are in the program, which mandates centralized curriculum standards for student learning in math and language arts in each grades K-12. Test results are used to rate school and teacher effectiveness.

But Common Core has come under fire from teachers unions and their political allies because of its emphasis on testing and teacher accountability. And Common Core faces criticism from conservatives because it seeks to require independent-minded states to use standards mandated at the national level. Bipartisan opposition to top-down education policy-making is why Congress scrapped the No Child Left Behind education law in 2015 and shifted school responsibilities back to the states.

These changing political waters suggest that if the Gates Foundation truly wants to advance public education, the last thing it should do is advocate national standards. Instead, it should urge states to copy what has worked in other states. This approach would be much more difficult to criticize than Common Core.

In liberal, pro-union states like California, an educational campaign that pointed to how much better the public education system is in liberal, pro-union Massachusetts could build momentum for change. The Massachusetts Education Reform Act of 1993, crafted with input from teachers, established standardized basic methods to assess the performance of students, teachers, administrators and superintendents and hold them accountable. While Massachusetts has clusters of struggling students in poor minority communities, its public schools are widely seen as America’s best.

In conservative, non-union states wary of national dictates, an educational campaign could emphasize how much better the public education system is in conservative, non-union Texas. Since 1984, the Texas government has passed a series of education reforms that — like those in Massachusetts — set up basic accountability requirements for schools and districts while tracking the performance of four student groups: whites, Hispanics, African-Americans and the economically disadvantaged. A 2015 Urban Institute report ranked Texas behind only Massachusetts and New Jersey in school quality in an evaluation that adjusted for student demographics.

Gates seeming to lose faith that Common Core can succeed will be music to the ears of people like Gov. Jerry Brown, who famously rapped the “siren song” of trendy school reform in 2011. But no critic can explain away the years of comprehensive success seen in Massachusetts and Texas. Whether you live in a red state or a blue state, no one should accept so-so schools. There is a better way.